Chlorination energy

Ozone (O3) is a powerful oxidant, and application to effluent treatment has developed slowly because of relatively high capital and energy costs compared to chlorine. Energy requirements for ozone are in the range of 10 to 13 kWh/lb... 

Application Inovyl s high temperature chlorination (HTC) is an energy-efficient process to produce ethylene dichloride (EDC) from ethylene and chlorine. Energy is conserved by using the exothermic heat of reaction to vaporize the EDC, thus product purification can be done by fractional distillation. Unlike with the LTC process, waterwashing the product to remove dissolved ferric chloride is not necessary. Therefore, no aqueous effluent treatment is required. 

Inovy Direct chlorination, high temperature chlorination Ethylene, chlorine Energy efficient process, product purity of 99.95%, low maintenance, no EDC washing 14 1995... 

Mixed plastics automobile shredded 3 wt% chlorine Energy and Environmental Research Corporation and US EPA, pilot scale, spouted bed fluidized regime ablative gasification, 500-800°C Fe203 active gasification catalyst and sorbent for HCl Petrochemical feedstocks 381b... 

S = Heat of sublimation of sodium D = Dissociation energy of chlorine / = Ionization energy of sodium = Electron affinity of chlorine Uq = Lattice energy of sodium chloride AHf = Heat of formation of sodium chloride. 

Figure Bl.6.8 Energy-loss spectra of 200 eV electrons scattered from chlorine at scattering angles of 3° and 9° [10]. Optically forbidden transitions are responsible for the intensity in the 9° spectrum that does not appear in the 3 ° spectrum.

Figure Bl.25.2 shows the XPS spectra of two organoplatinum complexes which contain different amounts of chlorine. The spectrum shows the peaks of all elements expected from the compounds, the Pt 4f and 4d doublets (the 4f doublet is iimesolved due to the low energy resolution employed for broad energy range scans). Cl 2p and Cl 2s, N Is and C Is. Flowever, the C Is caimot be taken as characteristic for the complex only. All surfaces that have not been cleaned by sputtermg or oxidation in the XPS spectrometer contain carbon. The reason is that adsorbed hydrocarbons from the atmosphere give the optimum lowering of the surface free energy and hence, all surfaces are covered by hydrocarbon fragments [9].

Chang J P, Arnold J C, Zau G C H, Shin H-S and Sawin H H 1997 Kinetic study of low energy ion-enhanced plasma etching of polysilicon with atomic/molecular chlorine J. Vac. Sc/. Technol. A 15 1853-63... 

Gillis H P, Choutov D A, Martin K P and Song L 1996 Low energy electron enhanced etching of GaAs(IOO) in chlorine-hydrogen DC plasma Appl. Phys. Lett. 68 2255-7... 

A/12 the dissociation or bond energy of chlorine, again twice the enthalpy of atomisation. 

Let us consider the formation of sodium chloride from its elements. An energy (enthalpy) diagram (called a Born-Haber cycle) for the reaction of sodium and chlorine is given in Figure 3.7. (As in the energy diagram for the formation of hydrogen chloride, an upward arrow represents an endothermic process and a downward arrow an exothermic process.)... 

Ah second ionisation energy for sodium (additional) +4561 A/13 enthalpy of atomisation of chlorine, x 2 (since two... 

AI14 electron affinity of chlorine, x 2 (two ions are formed) —728 A/15 calculated lattice energy —2539... 

The enthalpies for the reactions of chlorine and fluorine are shown graphically in Figure 11.2 as the relevant parts of a Born-Haber cycle. Also included on the graph are the hydration energies of the two halogen ions and hence the enthalpy changes involved in the reactions... 

Electron affinity and hydration energy decrease with increasing atomic number of the halogen and in spite of the slight fall in bond dissociation enthalpy from chlorine to iodine the enthalpy changes in the reactions... 

Bromine, like chlorine, also undergoes a photochemical chain reaction with hydrogen. The reaction with bromine, however, evolves less energy and is not explosive. 

Were we to simply add the ionization energy of sodium (496 kJ/mol) and the electron affin ity of chlorine (—349 kJ/mol) we would conclude that the overall process is endothermic with AH° = +147 kJ/mol The energy liberated by adding an electron to chlorine is msuf ficient to override the energy required to remove an electron from sodium This analysis however fails to consider the force of attraction between the oppositely charged ions Na" and Cl which exceeds 500 kJ/mol and is more than sufficient to make the overall process exothermic Attractive forces between oppositely charged particles are termed electrostatic, or coulombic, attractions and are what we mean by an ionic bond between two atoms... 

Compare chlorination of methane with lodina tion The relevant bond dissociation energies are given in the equation... 

Bromination of methane is exothermic but less exothermic than chlorination The value calculated from bond dissociation energies is AH° = -30 kJ Al though bromination of methane is energetically fa vorable economic considerations cause most of the methyl bromide prepared commercially to be made from methanol by reaction with hydrogen bromide... 

In the laboratory it is more convenient to use light either visible or ultraviolet as the source of energy to initiate the reaction Reactions that occur when light energy IS absorbed by a molecule are called photochemical reactions Photochemical techniques permit the reaction of alkanes with chlorine to be performed at room temperature... 

Carbon-Hydrogen and Carbon-Chlorine Bond Dissociation Energies of Selected Compounds... 

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